The invention relates to a device for observing the tube plate of a steam generator comprising parallel banks of tubes situated in an enclosure having at least one access situated opposite an interval between two adjacent banks, said device comprising an elongated member having a cross section whose transversal size is less than the width of the interval, insertable through the access and containing light guide means and an endoscope and finishing in a head provided with orientatable light deflection means associated with the endoscope and with the light guide means for illuminating and observing a same zone of the plate.
The invention is particularly (though not exclusively) suitable for visual inspection of the tube plate of steam generators used in PWR nuclear generating stations. For safety in use of the generating station, there should be no leak of the primary fluid, which flows along the tubes, into the secondary fluid which flows through the space defined by the tubes and the casing of the steam generator. Observation of the tubular plate on the secondary side of the steam generator supplies indications useful for operation and for safety and in particular makes it possible to monitor the condition of the base of the tubes of the bundle through which the primary fluid flows, the nature, the color and the location of oxides and sludge deposits and the presence of possible foreign bodies.
Visual observation devices of the above defined kind have already been constructed. In one type of steam generator frequently used in nuclear power stations, the enclosure is provided with different accesses; some of them, generally called "eye holes", are placed at a small distance from the tube plate, opposite the interval between two banks of tubes. A pole constituting the elongated member of the device may be introduced through the eyehole, between two adjacent tube banks, which allows the observation to be carried out at a distance and so prevents the operators from being exposed to radiation. The pole is stopped in successive positions in which the deflector means of the head are situated between two adjacent rows of tubes and the observation is carried out by scanning with the deflection means.
But, because of the small spacing between two adjacent rows of tubes, it is impossible to align the deflector means of the endoscope and of the light guide in the insertion direction. So as to keep nevertheless the possibility of effecting an observation directly under the endoscope, it has been proposed to place the orientatable deflector means of the light guide at the end of a laterally projecting light deflection tube. But this solution presents serious drawbacks. The lateral tube must be brought into a vertical position before the pole is moved and any oversight may damage the device, even cause the projecting part to fall into the steam generator; and it is not possible to observe both sides of the pole with a same instrument.
It is an object of the invention to provide an improved observation device; it is a more particular object to provide a device which makes it possible to observe the tubular plate on both sides of the elongated member while avoiding the presence of members beyond the width of the interval between adjacent banks.
For that purpose, the device has light deflecting means disposed within the cross-section of elongated member, substantially one above the other; the light deflection means are at a distance from the plate greater than the deflection means of the endoscope and the device further includes a fixed light guide for illuminating the zone of the plate in which the light beam coming from the deflection means of the light guide is cut by the deflection means of the endoscope.
The invention will be better understood from the following description of a particular embodiment of the invention and from the comparison thereof with a device of the prior art.